Bouncing back from an 18-point defeat in New Hampshire, Bush ran up a victory margin in the Palmetto State that exceeded all predictions and cast serious doubt on McCain's ability to recover.

With nearly complete returns tallied, Bush won a clear majority of the vote, defeating McCain by a projected 13 percentage points. Alan L. Keyes was a distant third, with about 5 percent of the votes cast.

Key to Bush's success was an all-out push by his campaign to turn out conservative Republican voters, and in particular members of the religious right, who backed him by overwhelming margins.

Bush told supporters in the state capital of Columbia that he was "honored and humbled by the huge victory we had in South Carolina."

"Tonight, there are only 263 days more to the end of Clinton-Gore," he said to cheers.

In a TV interview last night, Bush said he "did a good job of uniting our party."

The Texan, who assumed a much more aggressive style here, said he did "a better job as a candidate" than in New Hampshire and brushed aside criticism of his negative campaigning.

"I stand by what I did," he said on CNN. "I defended myself."

McCain, however, left little doubt that he regarded Bush's

bare-knuckle tactics as having been the decisive factor.

In scathing terms, McCain laced his concession speech with bitter references to his rival.

Saying he intended to "keep fighting clean," McCain told supporters in North Charleston that he "will not take the low road to the highest office in this land. I want the presidency in the best way, not the worst way."

He contrasted himself with Bush, suggesting that the Texas governor had let "ambition overcome principle." He linked Bush's campaign to "defeatist tactics of exclusion" by the GOP establishment that would lead to a Republican defeat in November.

McCain compared his record of reform to Bush's "empty slogan of reform" and portrayed the contest between himself and the son of the former president as a choice "between experience and pretense."

The fierce 18-day campaign in this state ended on a balmy day that helped draw record numbers of voters to polling places. By one estimate, the turnout may have reached 600,000, more than twice the previous record, set in the 1996 primary.

An unprecedented number of independents and Democrats, many of them lured by McCain's crossover appeal, cast votes in the Republican primary.

But Bush's "fire wall" in this state served its intended purpose, halting McCain's surging campaign behind a huge wave of votes from social and religious conservatives.

The size of Bush's victory once again makes him the front-runner in the Republican race and raises the stakes for Tuesday's primary showdown in Michigan.

McCain refused in a TV interview to concede that he must win Michigan to keep his nomination hopes alive. The latest polling shows the race there to be a dead heat.

"Michigan will be very important," the senator said. But "no matter what," McCain said, he will remain in the race at least until March 7, when 16 states, including Maryland, hold primaries or caucuses.

There was no Democratic contest in South Carolina yesterday, and the number of non-Republicans who cast ballots in the primary was unusually high. According to exit polls, about 40 percent of the total vote came from non-Republicans.

McCain claimed that he carried Charleston, the state's largest city and a Democratic stronghold. Slightly less than 10 percent of the vote was cast by Democrats, in line with pre-election estimates.

Bush took about one-third of the independent vote, exit polls showed, then rolled up lopsided margins among Republican voters.

According to election-day interviews of voters leaving polling places around the state, Bush swept the votes of those who identified themselves as Republicans by a 68-26 percentage point margin.

"It's very difficult to construct a strategy of winning a Republican nomination when you're going to lose Republican voters by 40 points," said Whit Ayres, a Republican pollster who is neutral in the race, referring to McCain's failure to generate more support among Republicans.

Bush's support from religious conservatives, who favored him by a nearly 3-to-1 margin, was an essential element in his victory.

The Bush campaign's outreach to Christian conservatives was spearheaded by Ralph Reed, former executive director of the Christian Coalition and now a Republican consultant.